THE LIVING SUBSTANCE. 



91 



optical network, makes such false striations which really have 

 little to do with the true and common structural relations of a 

 strial sort. In sections, a tearing, or displacement in shrinking, 

 of the visco-fluid lamellar substance may cause a marked, but 

 false, seeming of structural striation. However strongly mesh- 

 work lines extend in a given direction, caution must be used in 

 inferring tension, by osmosis or what not, in that direction, for 

 a marked, and seemingly simple and direct, striation in one 

 optical plane may express diverse strains in other directions. 



In tracing many optical striations of protoplasm along lines 

 of, so-called, optical emphasis, I presently became aware that 

 besides these were others of a different origin and nature, 

 having marked specific characters. Here too it seemed that 

 though a true word had been spoken and a strong word, yet, 

 as in the case of the foam structure, it was not the " master- 

 word " of the situation. Comparing the new sort of striations 

 with those just described, it seemed to me that certain defi- 

 nite physical, and psychological, or optical, qualifications of 

 these latter did not apply to the former. If I am mistaken in 

 supposing these not capable of being grouped with products of 

 purely physical, or mechanical, lamellar extension, the physi- 

 cists will not leave the error long uncorrected. 



Such striations have a basis of actual physical difference in 

 mass and character of the continuous, or interalveolar, sub- 

 stance, which causes them to have marked optical emphasis. 

 Many of them were correlated with contractile activities, and 

 were found to depend not only upon a characteristic passive 

 arrangement of the continuous substance, but upon intermittent, 

 or rhythmic, states and physical modifications of this. These 

 were manifested optically by rhythmical, or intermittent, changes 

 in its mass, density, refractive quality, viscosity, and position 

 in the mass, or area. Striation may exist before and after con- 

 tractile function, but the latter always produces in the substance 

 either optical striation of a visible structure ; or optical changes 

 which are to be correlated with a similar structure beyond our 

 reach ; or increased emphasis of an existing striation. 



There is another striation which may exist without being 

 associated with organized contractile function ; this is a local 



